It is known that electrical power may be harvested from renewable energy sources, such as sunlight and wind, using photovoltaic arrays (also known as solar panels) and wind turbines, respectively. It is also known that photovoltaic arrays stop producing power at night, and that energy production is significantly reduced when cloud coverage interrupts or obscures the sunlight. Wind turbines, on the other hand, may continue to produce power as long as the wind is blowing, and therefore may be used in conjunction with photovoltaic arrays to increase and/or stabilize the power output from an alternative energy power plant, particularly at night and during overcast days.
With few exceptions, power plants produce alternating current (AC) synchronized in frequency and phase with the power grid. However, photovoltaic arrays naturally produce direct current (DC) power output when exposed to sunlight. Thus, an inverter is used for transforming or converting the DC output from the photovoltaic array to an AC signal appropriate for coupling to the power grid. Wind turbines can generate AC power output, but the frequency and phase of the wind turbine output depends, respectively, on the rotation speed and position of a rotor within the turbine generator. Therefore, the AC power produced by the wind energy system is typically rectified to produce an intermediate DC power signal. The DC power signal is then transformed to AC via a line-commutated inverter to match the line frequency and phase of the grid.
Each inverter adds costs to the power system in terms of component expense, power penalty, and complexity. Therefore, systems and methods are needed for converting power from wind and solar sources to a form that can be readily utilized by the power grid while reducing the component count and expense associated with redundant inverters. Systems and methods are also needed to provide hybrid wind-solar inverters.